I am finishing the engine rebuild and about to fit up the cams. The car is a TT auto. Are the cams the same for a manual and auto engine? If there are any differences what would be the benefit or downside of fitting these cams to an auto trans car?
Auto exhaust cams are slightly shorter duration than the manual (only on TT engines). I'm definitely not an expert in the field but I think that gives you cooler/cleaner exhaust gasses but hotter combustion temps, this means less top end power. If you're still using standard auto turbos auto cams are probably fine, upgraded turbos you'd want manual cams or aftermarket.
Keep the auto cams but run manual turbos or better. The lower duration of the intake cams will give you slightly better response at the cost of a little top end.
I've got auto cams in my car and recently went from high-flowed auto turbos to GT525s with a manual housing. Like you, I was worried that my auto cams were where the bottleneck in power was coming from. However after upgrading turbos, even with the auto cams power is responsive and pulls sooo much harder to red line - I even had to drop my boost slightly as I was coming close to maxxing out the 555cc injectors and AFM. Yet to dyno, but it feels like I've picked up an extra 30-40kw. I don't think you have anything to worry about
Have you keep everything in its origonal place ?? Lifters need to stay with the lobe they were broken in on Extract from Crane Cams If you are rebuilding an engine and plan to re-use the existing cam and lifters (in the same heads) it can be done, as long as the lifter goes back on the same lobe it is mated to. If the lifters get mixed up, they cannot be used, and a new set or reground set will be required. The new lifters would also have to go through the break-in procedure to mate to the old cam.
I had auto cams with highflow turbos and all the boltons. Responce and power below 4k was awesome. Above 5k power started to stagnate because of cams. Reasonable trade off for a car that very rarely saw above 5k.
I have been thinking about this and given that I am a Grey Beard most of my driving will be more cruising oriented with the occasional squirt and other club type activities. However in saying that the motor does have bigger turbos's T28 and injectors, and all cam followers are matched as were the valves. Modified dumps and 3 inch exhaust. So would the consensus be, leave in the auto cams or go for the manual cams?
INCORRECT The lifters are concave and as the cam lobe wipes across the lifter face it spins it ever so slightly - this is so that it doesnt just sit there pounding away in the same spot but rather a new position on the lifter everytime its actuated Breakin of new cams and new lifters is critical - special procedure New lifters on old cams is acceptable - follow breakin procedure None mated lifters on old cams = BAD Old lifters on new cams = BAD
New lifters on old cams is acceptable - follow break in procedure I am unaware of this break in procedure, could you be more specific please. So do I leave the auto cams in and be done with it?
I have to correct myself - because I'm old all my work in the past has been with pushrod engines and can kill lifters or cam lobes if not run in properly The following is a quote Modern overhead cam engines running on bucket followers use hardened steel as the bucket material and these are ground flat not radiused although there is still an offset to ensure rotation. Engines with flat faced bucket lifters made of hardened steel - if unworn, will usually be ok to use with a new cam This is the break in procedure for a flat tappet cam and follower (pushrod engines) out of interest - pick and use what you like out of it I certainly will be using the Moly on the lobes and buckets when I reassemble my engine The break in procedure is not just to "match" the follower to the cam lobe as is commonly thought. It is also to work harden the surfaces for which cast iron is an excellent material. The high point loadings rapidly compress the surface skin of the lobe and follower and create a hardened skin which then resists wear. All cam systems wear at a given rate during their service life and the rate of wear depends on lubrication, material hardeness, regularity of surface finish and other factors. The aim is to reach a rate of wear at which the freshly exposed metal work hardens quick enough to resist further wear. If the follower stops rotating or the lubrication boundary fails then wear takes place faster than hardening takes place leading to catastrophic failure. Break in procedure is to coat the running surfaces with molybdenum disulphide lube and then run at 1500 to 2000 rpm for 15 to 20 minutes. Low speeds create high point loadings and high speeds create rapid wear rates. Intermediate engine speeds allow work hardening to take place without excessive point stress on the parts. 99% of cam failures are due to inadequate break in procedures.
Out of interest - who has put new cams in lately ?? What is on the install information card Do they have a start up procedure Do they supply Cam lube for assembly
It can be a hit and miss operation using old followers on new cams. Vice versa and verse visa blah. Many people report no problems and just drive on but there are also stories of cam lobes coming apart. Rodos quoted comment: Is quite true depending on that seemingly insignificant, but crucial 2 words "if unworn"!!! Those follower faces and matching cam lobes can be worn unevenly as a pair as a result of prolonged engine abuse, infrequent regular maintenance and so-on but left together will run on for years. IMHO, EXTREME caution and special attention to inspection should always be exercised when fitting mixed (new/used/unmatching) cam/follower components. Just because it appears ok at first glance does NOT mean the combination of slightly dished followers and/or convex'ed cam lobes mixed will happily run together for long!!! Slightly dished followers, nice new and flat cam lobes = full spring loading over a tiny contact area = exceed oil boundary layer = metal on metal = extreme heat and wear = possible cam lobe failure. Attention to detail here is the key. Just me. E
I have NEVER had a problem using used lifters with new cams, providing the lifters are cleaned, the hardening is not stuffed on the lifter top. I also check the lifter tops for dish before reassembly. I get a good set out of about 3 used engine sets.
I wouldn't expect anything less from you Tek-man, which is indirectly my point. The last comment sums it all up perfectly as you have sorted thru your stocks of followers etc and found followers that are not suitable and might cause issues. The message should be clear enough for all to see. E
Given that the thread is going somewhat off topic I have decided to take all input into consideration but feel that the response by SRB2NV is closest to what I am seeking. I will stay with the auto cams and larger turbo's and injectors.
